Watchwork mechanisms



y 30, 1963 v R. STRAUMANN 3,

. WATCHWORK MECHANISMS Filed Oct. 3, 1960 2 Sheets-Sheet 1 l7 /2 13mmREINHARD STRAUMANN BY WW 'ATTORN EYS y 9 R. STRAUMANN 3,099,128

WATCHWORK MECHANISMS Filed Oct. 3. 1960 2 Sheets-Sheet z I, I p

mvamow i5 REINHARD SIRAUMANN' BYWW M'roRN EYS Claims priority,

This invention relates to watchwork mechanisms and has for an object toreduce the liability of the mechanism-and especially the oscillatorysystemto damage by shock and lack of lubrication. The most delicate partof a watch is its oscillatory system. The relatively high speeds whichmembers of the oscillatory system perform necessitate considerable carein the production of the bearings. In order to protect the small pivotsand arbors from damage, a variety of shock absorbing devices has beendeveloped. Substantially these rely on an elastic mounting of the jewelswhich permits them to yield when shocks exceed given limits sothat somemore robust part of the arbor or component supported thereby can beengaged by a suitably formed abutment surface. Undoubtedly such devicesmay often prevent fracture or bending of a balance staff or pivot.

The principal disadvantage of all these more or less complex safetydevices is that the play of the pivot shank is necessarily small. If oilor particles of dust or contaminates get to the elements of a shockabsorbing system, additional friction results which adversely affectsthe movement of the watch, because the free oscillation of the balanceis disturbed. On the other hand, the restricted amount of play of thepivot shank may cause the oil to be squeezed out of the bearings by therelative motion between the bearing elements, allowing the bearings torun dry and to seize.

The present invention is based on the realization that the forces whichact on the balance staff are proportional to the mass of the completebalance. Considering this known fact in a watch mechanism according tothe present invention the balance has a relatively thick stafi but asmall total mass. Since the mass of the balance is related to thefrequency of its oscillations, the present invention is particularlyapplicable to watches in which the balance performs between 17,000 and22,000 half-oscillations per hour. Furthermore, since the mass of thebalance also depends upon the size of the watch, it is proposed to makethis mass functionally dependent upon the internal diameter of thespring barrel.

In a mechanism such as a wrist watch, according to the presentinvention, and in which the balance wheel performs between 17,000 and22,000 half-oscillations per hour, the balance sta'lf is made of anage-hardenable alloy containing a major proportion of either Fe-Ni,Fe-Co, Fe-W, Fe-Ni-Co or Ni-Co, which permits the finished staff to beage-hardened to give a tensile strength exceeding 200 kg./ sq. mm, and aVickers hardness between 600 and 750-preferably between 650 and 700-andthe mass of the'entire balance doesnot exceed the limits of maximum massM (measured in milligrams) for given internal diameters D (measured inmillimeters) of spring barrel according to the following table:

United States Patent I 3,099,120 Patented July 30, 1963 Practicalembodiments of the present invention will now be particularly described,by way of example only,

with reference to the accompanying drawings in which: FIGURE 1 is acurve relating limiting values of balance wheel mass to internaldiameter. of the spring barrel;

FIGURE 2 is an exploded view of a wrist watch, and FIGURE 3 is an axialsection through an entire balance. The several parts of a watch in whichthe balance performs between 17,000 and 22,000, and more specifically18,000 or 19,800 or 21,600 half-oscillations per hour, are clearly shownin FIGURE 2. The spring barrel'l has a cover 1a and is coupled to theescape wheel 2 by three gear wheels, 3, 4 and 5. Normally the springbarrel 1 will be large enough to fill the whole of the available spacebetween the outer edge 16 of the basepl-ate 17 and the centre 18. Inother words, the overall diameter of the spring barrel will be onlyslightly smaller than the overall radius of the watch movement. Theescapement lever is sho at 6 and the balance as a unit at 7. As will beseen by reference to FIGURE 3, the complete balance comprises a rim 8which is integral with the spokes 9 and the hub 10 of the wheel. The hub10 is mounted on a stalf 11 which also carries the roller 12 and acollet 14 for attachment thereto of the hairspring 13. The pivots 15 ofthe stall 11 have a slightly conical taper, the cone angle lying between3 and 15, and preferably being approximately 7. The staff should be asinelastic and as rigid as possible.

It is necessary that the staff consists of an age-hardenable alloycontaining a major proportion of either Fe-Ni, Fe-Ni-Co, N-i-Co, Fe-W or-Fe-Co, which permits the finished staff to be age-hardened, and thatits tensile strength should exceed 200 kg./sq. mm., and its Vickershardness number should be between 600 and 750, preferably between 650and 700.

Alloys based on Fe-Ni may have the following compositions:

Alloys based on Fe-Ni-C'o may comply with one of the following analyses.

Type 3: Percent Ni 10-63 Co 5-50 Fe up to 20 The Ni-Co-Fe groupconstitutes from 57-80% of the total alloy composition.

Percent Cr 10-20 Mo 5-10 W The Cr-Mo-W group constitutes from 20-30% ofthe total alloy composition;

Percent Be 0.1-3 Ti 0.1-3 Al up to 6.5 Nb up to 5 C 0.01-0.6 Mn up to 6Si up to 1 V up to 6 Cu up to 6 The Mn-Si-V-Cu group constitutes up to8% of the total alloy composition.

ri i??? l Co 18-50 Fe up to 25 The Ni-Co-Fe group constitutes from52-85% of the total alloy composition.

Percent Cr 10-20 Mo 1-10 W up to 10 The Cr-Mo-W group constitutes from11-30% of the total alloy composition.

Percent Be up to 3 Ti up to 3 C 0.05-0.6 Al up to 5 Nb up to 5 V up to 6Cu up to 6 The Be-Ti-C-Al-Nb group constitutes up to 6% of the totalalloy composition.

At least one of the elements beryllium, titanium, aluminum and niobiumshould be present in the following minimum percentages: Be 0.04%; Ti0.2%; A1 0.1%; Nb 0.1% or a corresponding mixture thereof.

The alloys containing a major amount of Ni-Co may have the followingcomposition:

" 8; i of Cr 10-20 Mo 5 W 5 0.2-0.4 T-i 0.8-1.2 C 0-0.05 Mn+Si 2 Ni30-40 Suitable alloys based on Fe-W may have the following compositions:

Percent Cr 2-10 V 0-1 C 0.5-1.5 Si 0.1-1.0 Mn 0. 1-1.0 Ti 0-3 Be 0-0.5Nb 0-3 Fe Remainder The balance staff 11 is produced for instance asfollows: A wire consisting of one of the alloys of types 1 to 5 isannealed at about 1100 C. and then quenched to room temperature. Theresultant wire, which is still soft, is cold worked, by rolling ordrawing or both, until its tensile strength exceeds 200 kg./sq. mm. Onan automatic lathe a balance staff is now machined out of this wire.When the staff has been machined it is subjected to a thermal treatmentwhich may last between a quarter of an hour and six hours and whichinvolves temperatures between 200 C. and 600 C. This imparts to thestalt a Viokers hardness between 650 and 700. Finally, the staff isground. Alternatively, the staff may be turned after having beenthermally treated or it may be ground before being thermally treated.

If an alloy of type 6 or 7 is used, then the initial material must behot worked at a temperature between 600 C. and 1000 C. and then annealedat an elevated temperature and quenched. From this material the staffmay be produced. This is finally submitted for from 10 to 60 minutes toa heat treatment between 400 C. and 700 C. If desired, the staff may beproduced after the heat treatment has been performed.

The finished staff is now provided with a light-weight rim, that is tosay with a rim which is sufliciently light for the mass M of the entirebalance to be less than the mass defined by the limiting curve 19 inFIG. 1. Hence, the mass M of the balance of a watch having a springbarrel 1 with an internal diameter D of 8 mm. may be, for instance, 50mg, a value which is identified in FIG. 1 by the point 20. A balance ofthis low weight can be obtained by making the rim from an alloy of lowspecific gravity, such as an aluminium alloy, or by suitably designingits dimensions, particularly the cross-sections of its spokes and rim.The aim is always to obtain the largest possible moment of inertia for agiven weight.

The widely accepted view that watches fitted with a relativelylight-weight balance wheel are more likely to suffer from irregular timekeeping has been found to be incorrect. On the contrary, it has beenascertained that a watch with a light-weight balance, that is to'say abalance weighing less than defined by the limiting curve 19 in FIG. 1,is superior to a watch with a conventional balance wheel, both withrespect to its shock resistance and to its time-keeping accuracy.

In wrist watches the friction in the bearings of the balance staff isrelatively high. It depends upon the mass of the balance. Friction atthe pivot is especially high when the staff is horizontal and lower whenthe staff is vertical. This friction, which depends upon the attitude ofthe balance causes the amplitude of the oscillation to vary independence upon the position in which the watch is carried. Thereby thetime-keeping of the watch will be altered.

A further decrease in amplitude, and hence a further disturbance of theisochronism of the watch, arises as a result of the decrease in torquetransmitted by the main spring when it runs down.

These two factors, which additively affect the timekeeping properties ofthe watch, are both reduced in effect if a balance of light weight isemployed. On the one hand, friction depending on mass is less and, onthe other, the energy requirements of the oscillating member arereduced. Consequently, the torque delivered by the main spring can besmaller and the spring itself may be thinner.

If the original volume it is the It will therefore be readily understoodthat a shockproof mechanism according to the present invention is ofsubstantially simpler construction than one fitted with conventionalshock-absorbing means, and since the lubrieating problems associatedwith the latter are removed and the oscillatory mass is less, the faultliability is reduced.

I claim:

statf consists of an age-hardenahle alloy containing a ma or proportionof a member selected from the group consisting of Fe-Ni, Fe-Co, Fe-W,Fc-Ni-Co and Ni-Co and has a tensile strength exceeding 200 kg./sq. mm.

meanest-abs 1 p fmznt according to claim 1 wherein the balance staffCOIISlfits of an alloy of the following composition:

Percent N1 10-63 Co -50 Fe up to 20 Cr Q -20 Mo 5-10 W 5-10 Be 0.1-3 Ti0.1-3 1 up to 6.5 Nb up to 5 C 0.01-0.6 Mn up to 6 Si up tol V A up to6Cu' up to 6 the sum of said Ni-Co-Fe percentages constituting from to80%, the sum of said Cr-Mo-W percentages con- .tuting from 20-30%,

F ercentages constituting up to 8% of the total alloy composition.

3. The improvement according :to claim 1 wherein the balance staffconsists of an alloy of the following composition:

and the sum of said Mn-Si-V-(hl Percent Ni 50-68 Fe '10-25 Cr 12-25 Mo+W5-10 Be 0.6-1.2 Ti 0.6-2. Si+Mn upto 3 4. The improvement according toclaim 1 wherein the balance staff consists of an alloy of the followingcom- 5. The improvement according to claim 1 wherein the balance statfconsists of an alloy of the following composition:

Percent Ni 13-65 Co 18-50 Fe up to 25 Cr 10-20 Mo 1-10 W up to 10 Be upto 3 Ti up to 3 A1 up to 5 Nb up to 5 C 0.05%-.6% V up to 6 Cu up to 6the sum of said Ni-Co-Fe percentages constituting front 52 to and thesum of said Cr-Mo-W constituting 6. The improvement according to claim 1wherein the balance staff consists ot an alloy of the followingcomposition:

Percent Co 20-40 W 15-25 Cr up to 20 Mo up to 6 V up to 6 C 0.05-0.2 Si0.1-1.0. Mn (1.1-1.0 Ti up to 3 Be up to 0.5 Nb up to 3 Fe Remainder 7.The improvement according to claim 1 wherein the balance staif consistsof an alloy of the following com- Percent Be up to 0.5 Nb up to 3 I FeRemainder 8. In a watchwork mechanism, such as a wrist watch, having aspring barrel with a spring of substantially the maximum energy for theinternal diameter of said barrel and a balance including a balance staffmounted in substantially non-resilient bearings and adapted to performbetween 17,000 and 22,000 half oscillations per hour, the improvementwhich comprises that the balance stalf consists of a high strengthmaterial having a tensile strength exceeding 200 kg./sq. mm. and aVickers hardness number between 600 and 750, and that the mass of theentire balance does not exceed a maximum value M measured in milligrams,for a given internal barrel diameter D, measured in millimeters, asfollows:

D Mm 1) M D M... 2 8) 8-) References Cited in the file of this patentUNITED STATES PATENTS 15 1,333,161 Coats et a1. Mar. 9, 1920 2,496,248Jennings Jan. 31, 1950 2,622,021 Demirjian et al. Dec. 16, 1952

1. IN A WATCHWORK MECHANISM, SUCH AS A WRIST WATCH, HAVING A SPRINGBARREL AND A SPRING OF SUBSTANTIALLY THE MAXIMUM ENERGY FOR THE INTERNALDIAMETER OF SAID BARREL AND A BALANCE INCLUDING A BALANCE STAFF MOUNTEDIN SUBSTANTIALLY NON-RESILIENT BEARINGS AND ADAPTED TO PERFORM BETWEEN17,000 AND 22,000 HALF-OSCILLATIONS PER HOUR THE IMPROVEMENT WHICHCOMPRISES THAT THE BALANCE STAFF CONSISTS OF AN AGE-HARDENABLE ALLOYCONTAINING A